Method of recording sound



Oct. 9, 1934. wrr I 1,976,560

METHOD OF RECORDING SOUND Filed Sept. 6, 1950 INVENTOR:

Patented Oct. -9, 1934 UNITED STATES PATENT OFFICE METHOD or ascoanmo SOUND Application September 6, 1930, Serial No. 480,059

14 Claims.

My invention relates to phonographic apparatus and it has particular relation to sound-record tablets and methods or recording sound thereon.

The desirability of providing a sound-record I tablet for home-recording has long been recognized. Such a tablet, preferably, should be relatively immune to rough handling, either before or after the sound is recorded, yet, at the same time, it should be sufficiently impressionable to 10 enable satisfactory recording with minimum stylus-pressure; These requirements are, obviously, conflicting, and, previous to my invention, were not met by any record-tablet with which I am familiar.

An object of the invention is, therefore, to provide a record tablet blank and apparatus to be used therewith; in home-recording, which will overcome'the difficulties noted above.

Further objects of the invention are to provide an improved method of making a sound record on a tablet which is capableof being directly played therefrom a plurality of tim o pr v improved apparatus for carrying out the method of recording and reproducing sound from the rec- 35 0rd; and to provide a novel and improved soundrecord tablet.

Further objects of the invention are to provide an improved and simple process of making sound records, adapted to be practiced by persons uno skilled in the art of record making, and improved apparatus for carrying out the process.

Further objects of the invention are to provide a method and apparatus whereby an original rec- 0rd of sound may be made upon a non-metallic tablet of permanent or semi-permanent material and from which the recorded sound may be reproduced immediately or at any time thereafter. Further objects of the invention are to provide w a method whereby an original and permanent or semi-permanent record may be made on a blank of a materialhaving surfaces of cellulose compounds, such as the nitrate or acetate, for example, and apparatus for carrying forward the i5 method.

A further object of the invention is to provide an original sound record of permanent or semipermanent nature on a non-metallic record tablet reproducible directly therefrom a plurality of times.

Another object of the invention is to provide a method of home-recording sound vibrations in the walls of a preformed groove, such that there 5 will be little resistance, by the m te of t k record tablet,'to the vibratory movements of the recording stylus. 5

Still another object of the invention is to provide apparatus for making sound records, including a stylus and a record tablet having a pre- 00 formed groove therein for guiding the stylus and providing surfaces for receiving the record, impressions, the groove and stylus being so related and of such characteristics that there will be slight resistance, of the record material, tothe vibrations 'of the stylus during recording as compared with that of recording apparatus heretofore known.

A further object of the invention is to provide a method of home-recording of sound vibrations, in a pre-formed groove of a record tablet, such that there will be very little bearing contact of the recording stylus with the record surfaces, during recording, as compared with recording of this character heretofore known. 7

A further object of the invention is to provide apparatus for use in home-recording, including a pre-grooved tablet and a stylus guided by the groove in recording, the groove and stylus being of such characteristics that there will be a very little bearing contact between the stylus and tablet surfaces during recording.

A further object of the invention is to provide a method of recording, in the groove of a pregrooved tablet, with a'stylus vibrated transversely of the groove, such that the record will be impressed by the stylus on the sides of the groove, below the surface in which the groove is formed and spaced from the bottom of the groove, and such that the record will be made with a small bearing contact between the stylus and record tablet, during recording, as compared with that in recordingheretofore known.

I have found by experiment that an immediately reproducible original sound record, capable of satisfactory fidelity in reproduction and of permanent or semi-permanent nature, may be made in a non-metallic tablet by, first, providing the tablet with a guide groove and then making a sound record upon the side walls of the groove below the surface of the tablet in which the groove is formed and suiliciently short-of the bottom of the groove to provide a small bearing surface only between the recording point of the stylus and the side walls of the groove.

The record so formed is preferably so made upon the defining edges between the surface .of

the tablet and the side walls of the groove, as to appear both in the surface of the tablet and in the side walls, the said record extending in the the blank to be made of moldable substances other than metal.

Further objects of the invention, therefore, are to provide apparatus and a method of recording for effectively confining the record impressions to the upper or outer fraction of the walls of a groove and for so recording the sound upon the defining edges between the surfaces of the tablet and the side-walls of the groove that it lies below the surface in which the guide-groove it formed and between the two parallel surfaces of the tablet.

One way of accomplishing the aforementioned objects is to use, in connection with a pre-formed guide groove in the tablet, a stylus having a sound-record making portion and a portion or portions adapted to rest on the sound record tablet in such manner as to prevent the sound-record making portion of the stylus from projecting into the guide groove further than the sound-record depth desired.

While cellulose compounds, as indicated above,

' are preferred, the record tablet may be made of any'suitable material which is hard enough to stand up under a reasonable amount of handling and repeated playing and yet yieldable enough to readily take an impression, under the impact of the delicate vibrations of a recording stylus, operating within the groove as indicated above, and which is of such character that the sound recorded may be reproduced with a volume and clearness favorably comparable with that from known commercial records.

Cellulose nitrate .or acetate and combinations therewith, mentioned above, have been found suitable to this end, and a tablet made therefrom, when properly pre-grooved and subjected, as above, tothe vibrations of a stylus will, without further preliminary treatment, be capable of taking a sound record impression which may be immediately reproduced and which will stand up under repeated playing and other handling of the tablet.

Furthenby so making the record in the sidewalls of the groove, pie-formed in a record tablet, I

that it lies in the defining edges between said walls and the surface of the tablet in which the groove is formed, resistance, by the material of the tablet, to the 'vibratorymovements of the stylus is considerably minimized as compared with that in known methods of recording. a

The guide-grooves may be formed in any suitable manner as by softening the material of the blank tablet and then, or simultaneously therewith, pressing the blanks between dies having groove-forming ridges thereon. Cellulose nitrate or acetate can be conveniently softened by heating and, when heated to a pliable condition, it will yield to pressure sufliciently to permit of being formed. in the manner as stated.

After pressure has been applied for a suitable length of time and in a suitable amount, say

about 1000 lbs. per square inch, the dies with the tablets there-between. are cooled before the tablets are removed, which cooling may be facilitated by the use of a suitable water cooling system. The tablets so cooled may then be removed from between the dies and trimmed'after which they are ready to receive the record impression or to be stored for future use.

The shape of the groove formed in the tablet is preferably such that the side walls thereof will intersect the surface at a sharp angle.

It is preferable also that the land between the various turns of the groove shall be wider than the groove in order to prevent pushing of the material, in recording, out into adjacent turns resulting in echoes. A suitable width of the land is about one and one half times the width-of the groove.

A suitable stylus construction for recording in this manner may comprise a shank having a blunt recordingend provided with a limiting portion of sufficiently greater width than that of the guidegroove that it will rest on the surface of the disc and at all times in contact with the marginal edges of the groove and a tip-end portion extending into the groove for a fraction only of the depth thereof for guiding purposes and for making the record impressions. This recording end may be spherical in contour and the record making portion thereof may be just below and in continuation of the limiting portion.

The stylus, when in this form, should be pressed downward during recording by sufiicient weight to insure the proper impression in the particular material of the tablet. Where the tablet is of celluloid or other cellulose compounds, a weight of about two hundred grams is desirable. With this .weight, when no sounds are being recorded, the

stylus, as it travels in the groove, causes the margins of the groove to be uniformly deformed to a slight extent. Any great augmentation of this weight tends to cause the stylus to sink too far into the material and a materially diminishedv weight tends to cause imperfections resulting in undesirable noises in the. reproduction of the sound record. For tablets of other materials the weight necessary may be determined experimentally.

After the sound record has been'made on the upper edges of the walls of the groove the record tablet requires no further treatment, since, as indicated above, no shavings or crumbled particles have been formed in the process, and the sound record may be immediately reproduced by the use of the same stylus or one similar to that with which the record has been made. It will, of course, be apparent to those skilled in the art to which my invention pertains that, during the reproducing process, the pressure of the stylus against the record should be maintained materially less than during the recording process. If this is not done, the previously made sound record will be substantially wiped out by the stylus and satisfactory reproduction will not be had. Many ways for changing the stylus pressure will be apparent and no necessity is seen for describing any of them in detail.

Additional'objects of my invention will become evident from the following detailed description,

taken in conjunction with the accompanying drawing in which:

Fig. 1 shows a stylus, connected to an ordinary phonograph pickup" resting on a. tablet as in the recording or reproduction of sound.

Fig. 2 shows, on an enlarged scale, one form of a ne dle in relation to the guide groove in a rec- Ill tip before plating will .be of about .005".

' ord blank, the latter and the tip of the needle being shown in section.

Fig. 3 is an enlarged fragmentary perspective view of a tablet, showing guide-grooves formed therein, and a record impressed on the sidewalls of one of the grooves.

Fig. 4 is an enlarged fragmentary plan view of a record tablet herein; described illustrating the action of the stylus on the record groove from a condition prior to recording to a condition after recording.

Referring to the drawing, the apparatus disclosed therein is as follows:

The stylus used in recording, as outlined above and in the form shown, has a shank a, and (see Fig. 2) a blunted spherical tip end I), which is the effective record making portion, and it is preferably chromium plated as at 0, upon a base e ordinarily of steel or soft iron. The stylus shank may also have a portion d which is so tapered toward the recording end b as to provide an angle of about 60 between diametrically opposite elements of its surface. The tablet is provided with a pre-formed guide-groove f that,.preferably, is about .0015" deep and about .005" wide, and is arranged on the disc in a spiral having about eighty-six turns to the inch, leaving sufficient land therebetween for lateral excursions of the stylus therein without deforming adjacent turns with resulting objectionable distorted sound effects. The record tablet may be solidly formed of cellulose compounds or other suitable compositions, or it may consist of a fibre or other suitable core is with suitable impressionable surfacing material g, superimposed thereon, such as the cellulose compounds referred to above.

The stylus, as herein before indicated, should' have a diameter at its spherical tip sufficiently greater than the width of I the guideggroove to cause the stylus tip to rest on the surface of the tablet, spanning the groove, and should have a portion extending into the groove for guiding and recording purposes but held out of contact with the bottom thereof.

A stylus tip of about .006" radius is substantially correct for the above groove-dimensions and it has been found effective for maintaining the recording portion of the tip in the upper portion of the groove. The chromiunr plating on the working end of the stylus is of a suitable thickness to enable it to stand up under the rigor of recording. A plating thickness of about .001" is satisfactory, in which case the radius of the The stylus shank may be about /2 long and of about .068" diameter.

The sound record made on the upper or outer portions of the groove will appear somewhat as shown at h in Figs. 2 and 3 of the drawing, extending into the tablet and into the sidewalls of the groove a fraction of the way to the bottom thereof and also appearing in the surfaces of the disc in which the grooves are formed. The sound record is made, as stated above, on the edges defining the convergence of the parallel surfaces of the tablets and the sides of the groove, which are the most yielding portions of the tablet.

It should be-ob'vious, from a consideration of the foregoing, that my improved record and stylus may be utilized for home-recording either by causing the stylus to be directly actuated in response to sound waves or in response to electric current fluctuations representative of sound waves. Preferably, however, the stylus is carried by an electric pickup device such as is a constituent part of electrically energized phonographs since, as is well known to those skilled in the art, the operation of such pickup devices is reversible.

The excursions of the stylus during recording should never exceed the amount of deformation of the margins of the groove caused by the said stylus during non-recording intervals. This may be accomplished, of course, by properly limiting the amplitude of the currents representing the sound.

In order to further explain my invention, the

action of the stylus on a pre-grooved record tablet, from a condition before recording to a condition after recording, will now be described in detail in connection with Fig. 4 of the drawing, wherein g represents a fragmentary portion of the record tablet having a blank groove indicated at f.

Assuming, now, that the record tablet is ro-,

Deformation of the margins of the original groove in this manner, effects a widening or spreading thereof approximately to the extent indicated by the distance between the broken line r, representing the position of the original groove margins, and the widened margins s defining the deformed groove.

If, now, the. stylus is caused to vibrate transversely of the plane of the tablet, the margins of the' groove will assume an undulatory form as shown in the drawing between the points t and u.

At this point, it is to be observed that, atno time during such stylus excursions, does the extent of the excursions or deflections exceed the distance between the broken line 1' and the full line s. Consequently, even when a maximum excursion is made by the stylus in one direction,

the stylus will still remain in contact with the .my invention and have described a certain specific process and a specific product thereof, I am aware that various modifications may be made in either or all of these phases of my invention within the spirit and scope thereof, My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and the spirit of the appended claims.

I claim as my invention:

1. In the method of recording impressions on a tablet provided with a preformed groove, the step which comprises deforming only the marginal edges of said groove in accordance with said impressions.

2. The method of recording sound on a tablet causing said stylus to vibrate transversely of said groove in response to the sounds being recorded while simultaneously limiting the excursions of saidstylus that it always remains in contact with the edges of said groove.

4. The method of recording sound on a tablet provided with a preformed spiral groove which comprises causing a stylus to contact with substantially only the marginal edges defining said groove, moving said tablet under said stylus while maintaining contact therebetween with sufliclent to the sounds being recorded while substantiallypressureto cause said marginal edges to spread slightly below the" surface of the tablet and substantially on top of the edges defining said groove under the influence of said stylus and causing said stylus to vibrate transversely of said groove in response to the sounds being recorded while substantially limiting the excursions of s'aid stylus that it remains constantly-in contact with the marginal edges of said groove.

5. The method of recording sound on a record tablet provided with a preformed spiral groove which comprises causing a recording stylus, having a working tip whose diameter is at least twice the width of said groove, to contact with only the'margi'nal edges defining said groove, moving said tablet undersaid stylus while maintaining contact therebetween with sufficient pressure to cause saidmarginal edges to spread under the influence of said stylus, and causing said stylus to vibrate transversely of said groove in response limiting the excursions of said stylus to maintain it in constant contact with the marginal edges of said groove.

6. The method as set :iorth in claim '5 characterized in that the ratio-of the width of the preformed spiral groove to the diameter of the recording stylus at its working point is of the order of 1 to 3.

7. The method of recording sound on a tablet having a preformed spiral groove therein which comprises maintaining, substantially point'bearing contacts between a recording stylus and the marginal edges of the groove, and simultaneously forming, in only that portion of the walls of said groove immediately adjacent said marginal edges, undulations representing sound waves being recorded. I

8. In combination, a sound recording blank having thereon a preformed spiral guide-groove adapted to receive only in the marginal edges defining said groove, undulations corresponding to sound, and a recording stylus adapted to only contact with said marginaledges when tracking said groove.

9. The invention set forth in claim 8 characterized in that the stylus has a spherical tip.

10. The invention set forth .in claim 8 characterized in that the stylus has a spherical tip whose diameter is greater than the width of the preformed spiral groove.

11. In combination, a record blank of deformable material having thereon a'preformed spiral guide-groove, and a stylus of such size and shape that when it is caused to track said guide-groove it will contact only with the marginal edges defining said groove.

12. In combination, a record blank of deformable material having thereon a preformed spiral guide-groove, and a stylus adapted to be inserted in said groove, said stylus-having a tip portion which tapers along its axis from adiameter less than the width of said groove to a diameter greater than said groove width at a distance from its point which is less than the depth of said groove whereby, when said stylus is inserted in said groove, it engages the marginal edges defining said groove.

13. In combination, a record blank of deformable material having thereon a preformed spiral guide-groovesubstantially .0015" deep and .005 wide and a stylus having a tapered end portion terminating in a;spherical tip, said tip having a diameter slightly greater than the width of the groove at the surface of said blank whereby, when the stylus is disposed infthe groove it is supported by the marginal edges thereof and capable of deforming said. marginal edges to provide a record of impulses corresponding to sound if caused to move along said groove while being vibrated transversely thereof in response to said impulses.

14. A phonograph tablet having a preformed spiral groove thereon, said :groove having undulations, constituting a sound-record, only in the marginaledges defining said groove.

ALBER'HS HEWITT. 

